It is necessary in the manufacture of threaded parts that the pitch diameter be measured to assure that the parts have the proper pitch diameter. Measurement of the pitch diameter of externally-threaded parts has been done by the use of a threaded micrometer using threaded rolls or anvils matched to the thread of the part. Special calipers and threaded rolls, or anvils, are disclosed in U.S. Pat. No. 4,553,337. Other types of thread pitch diameter measuring devices include thread ring gauges and thread plug gauges; however, these merely indicate whether the part matches the gauge and do not indicate the precise measurement of the part.
Measurement of the pitch diameter of internally-threaded parts is even more difficult; however, it can be accomplished by the use of the thread gauge shown in the '337 patent or by the use of a special thread plug gauge which is used only for that particular inside thread diameter and thread type.
Various gauges have been used, but all that have achieved versatility of measuring internal and external threads on multiple thread forms and pitches have suffered from high cost.